Benchmark: JavaScript spread operator vs Object.assign to new object performance

Tests:

Using the spread operator
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = { ...firstObject, ...secondObject };
Using Object.assign
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = Object.assign({}, firstObject, secondObject);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using the spread operator
Using Object.assign

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

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Let's dive into the explanation of the provided benchmark.

**Benchmark Definition:**
The benchmark is designed to measure the performance difference between two approaches: using the spread operator (`...`) and `Object.assign` methods to merge two objects into a new object.

**Options Compared:**

1. **Spread Operator (Spreading)**:
	* Syntax: `{ ...a, ...b }`
	* Purpose: Creates a new object with properties from both `a` and `b`.
	* Pros:
		+ Concise and expressive syntax.
		+ Supports merging objects with arrays and other types of values.
	* Cons:
		+ May incur additional overhead due to the creation of a new array or other data structure.
2. **Object.assign()**:
	* Syntax: `Object.assign(target, source)`
	* Purpose: Merges properties from one or more sources into a target object.
	* Pros:
		+ Wide support and compatibility across browsers and Node.js versions.
		+ Flexibility to specify options for the assignment (e.g., `Object.assign(target, { ... })`).
	* Cons:
		+ Verbose syntax compared to spreading.
		+ May require additional processing steps.

**Library Used:**
None. The benchmark only uses built-in JavaScript features and does not rely on external libraries.

**Special JS Feature or Syntax:**
The benchmark utilizes the spread operator (`...`) feature, which was introduced in ECMAScript 2018 (ES2018). This feature allows for concise object merging using the syntax `{ ...a, ...b }`.

**Benchmark Preparation Code:**
The provided `Script Preparation Code` is empty, which means that no specific setup or initialization code is required to run the benchmark.

**Other Alternatives:**

1. **JSON Merge Patch (JMP)**: This approach uses a JSON merge patch format to represent the changes between two objects.
2. **Object Merging using `for...in` loop**: Another manual approach can be used, where you iterate over each property of one object and assign it to the target object if the key is not present in the other object.

Keep in mind that these alternatives are less concise and less expressive than the spread operator or `Object.assign()`, but they might offer better performance in certain scenarios.

Related benchmarks:

JavaScript spread operator vs Object.assign to new object performance (version: 0)

Comparing performance of: Using the spread operator vs Using Object.assign

Created: 3 years ago by: Guest

Jump to the latest result

Using the spread operator

Using Object.assign

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):